This invention applies to charge forming devices which are composed of one or more reciprocating plunger elements, as a pump means, and employ, as a fuel metering means, variation of the length of the fuel inlet stroke of the plunger elements. Examples of such devices are found in U.S. Pat. Nos. 1.834,224 and 1,912,367.
It is known in the prior art to meter a predetermined amount of fuel for injection into a combustion engine by filling a chamber of predetermined size and then pumping the fuel in the chamber into the engine. In such devices, a plunger is translated from an innermost position within the chamber to an outer position to permit a predetermined amount of fuel to enter the chamber. At an appropriate time in the engine cycle, the plunger is translated into the chamber forcing the fuel previously stored therein to enter the combustion engine.
The predetermined quantity of metered fuel for injection into the combustion engine is metered by limiting the maximum withdrawal of the plunger from the metering chamber. That is, the greater the degree of withdrawal of the plunger from the metering chamber permitted, the greater the amount of fuel that is drawn into the metering chamber. Similarly, the lesser the amount of withdrawal of the plunger that is permitted, the lesser is the quantity of fuel that can be drawn into the metering chamber when the plunger is in its withdrawn position.
The prior art employs a governor to limit the amount of withdrawal of the plunger thereby regulating the amount of metered fuel to be injected into the engine. In the prior art devices, after fuel is pumped from the metering chamber into the combustion engine, the plunger withdraws from the chamber the full permissible amount permitted by the governor at which time a new charge of fuel is drawn into the metering chamber. The plunger dwells in its outermost position until the appropriate time in the combustion engine cycle, at which time a cam forces the plunger into the chamber to pump the metered fuel within the chamber into the combustion engine.
It is frequently desired to adjust the governor while the engine is running to further limit the quantity of metered fuel to be injected into the combustion engine as, for example, to reduce engine speed. Since the plunger is normally in its withdrawn position and the metering chamber is normally filled with fuel except for the momentary period when the fuel is pumped from the chamber for injection into the engine, any attempt to adjust the governor so that the maximum amount of withdrawal of the plunger from the chamber is decreased necessitates movement of the plunger into the chamber against the force of the metered fuel stored therein. The resistance encountered by the plunger in moving into the metering chamber as the governor is adjusted is termed "hydraulic blockage".
Hydraulic blockage prevents adjustment of the governor, making the governor ineffective to control engine speed. This deficiency of the prior art makes governor control of engines employing charge-forming devices of the type herebefore described impractical. This is especially so with multi-cylinder internal combustion engines (and multi-rotor rotary internal combustion engines) wherein at any given moment the plungers in a majority, if not all, of the charge-forming devices associated with the respective cylinders or rotors will encounter hydraulic blockage upon an attempt to limit their withdrawal position by adjustment of a governor.